DNA STRUCTURE AND FUNCTION

Question 1

What is the structure of DNA

Answer 1

Double Helix

Question 1

Put the following in order from smallest to largest: nucleotide, genome, nitrogenous base, gene, nucleus, cell, codon, chromosome

Answer 1

nitrogenous base, nucleotide, codon, gene, chromosome, genome, nucleus, cell,

Question 2

Give an overview of the structure of DNA

Answer 2

1. Sugar phosphate backbone
2. Deoxyribose Sugar
3. Phosphodiester Bond
4. Base Pairs
   
   • with hydrogen bonds

Question 3

Explain nucleotides fully

Answer 3

• Building blocks of nucleic acids
• Made up of :
  1. Nitrogen containing group
  2. One or more phosphate containing components
  3. Sugars

Question 4

What is noticed about nitrogen contains groups / bases

Answer 4

• 2 rings that are fused together

Question 5

What is a purine

Answer 5

Consist of a 6 membered and a 5 membered nitrogen containing ring, fused together

• eg. Adenine and Guanine

Question 6

What is a pyridmidine

Answer 6

• Only have a 6 membered nitrogen containing ring

eg. Thyamine and Cytosine

Question 7

Explain Erwin Chargaff fully

Answer 7

• 1949
• Determined that despite the complexity of DNA
  • the amount of Adenine = amount of thymine
• amount of guanine = amount of cytosine

Question 8

Explain Wilkins and Rosalind Franklin

Answer 8

• 1950
• Made use of X-ray crystallography to determine the structure of DNA
• X-rays were passed through a DNA fibre and the images were “ caught “ on X-ray film by analysing the photographs which showed the shape of DNA

Question 9

Explain Watson and Crick

Answer 9

• 1953
• Put together model of DNA structure
• 2 strands ( made up sugar phosphate with nitrogen bases between ) coiled around one another to form double helix
• Sugar phosphates form the backbone of the helix and the bases are on the inside

Question 10

What are the bonds found in the DNA strand

Answer 10

Hydrogen; Covalent and Phosphodiester

Question 11

Explain hydrogen bonds fully

Answer 11

• Between bases
• 2 between A & T
• 3 between G&C

Question 12

Explain covalent bonds fully

Answer 12

• Sharing electron pairs between atoms
• Covalent bonds occur within each linear strand and strongly bond the bases; sugars and phosphate group

Question 13

Explain phophodiester binds fully

Answer 13

• Bonds between the 3’ carbon of one nucleotide and the 5’ carbon of the adjacent nucleotide
• String covalent bonds that hold sugar phosphate backbone together

Question 14

How do the strands run

Answer 14

Opposite directions

Question 15

Explain 5’ and 3’

Answer 15

5’ = bears a phosphate group

3’ = hydroxyl group

Question 16

Explain the ends of DNA in the nucleus

Answer 16

• DNA molecules in eukaryotic chromosomes is linear ( have 2 ends )
• Long stretches of nucleotides = telomeres
• 2000 Repeats of the sequence of 5’ GGTTAG 3’

Question 17

What is the function of telomeres

Answer 17

• Start of long but as cell divide they get shorter and short till critical length then that cell has to die
  
  • indicates cell age
• Protective caps

Question 18

Process that results in cell death

Answer 18

Apoptocis

Question 19

What are histones

Answer 19

Proteins that help package DNA strand

Question 20

Nucleosomes

Answer 20

Related to histones

Question 21

How is DNA used

Answer 21

To make proteins

Question 22

What do genes have

Answer 22

Info to make RNA which is then translated to make the protein

Question 23

What is the gene

Answer 23

Sequence of DNA nucleotides that codes for a specific proteins or RNA molecule and each organism has many genes

Question 24

What is a genome

Answer 24

All the genetic material in an organisms cells

Question 25

What are the 3 types of RNA

Answer 25

- mRNA ( messenger RNA ) -rRNA ( ribosomal RNA ) -tRNA ( transfer RNA )

Question 26

Explain mRNA

Answer 26

- Carries info that specifies a protein - Each gap of 3 mRNA bases in a row forms a codon, which is a genetic " code word " that corresponds to one amino acid

Question 27

Explain rRNA

Answer 27

- Combines with proteins to form a ribosomes, the physical location of protein synthesis - Some rRNA help to correctly align the ribosome and mRNA and others catalyse formation of the bonds between amino acids in developing protein

Question 28

Explain tRNA

Answer 28

- Molecules are connectors that bind an mRNA codon at 1 end and a specific amino acid at the other end - Their roles is to carry each amino acid to the ribosome at the correct spot along the mRNA molecule